A Monolithic Active Pixel Sensor as Direct Monitor for Therapeutic Antiproton and Ion Beams

The Mimotera, a monolithic active pixel sensor (MAPS) of crystalline silicon has been investigated regarding its ability to directly monitor antiproton and ion beams, and has been implemented as a beam monitor at the Antiproton Cell Experiment (ACE) at the European Organization for Nuclear Research (CERN). It has been proven to be a well-suited device for monitoring a spill of about 3 x 107 antiprotons only 500 ns long, on a shot-to-shot basis in real time without saturating. The commissioning of the Mimotera at ACE represents a major improvement, ensuring not only a more reliable data analysis due to exact profile measurements, but also speeding up the initial preparation of the experiment significantly. Moreover, it has been shown that the Mimotera behaves linearly as a function of intensity, as well as of the energy loss of a carbon ion beam at the Heidelberg Ion-Beam Therapy Center (HIT). The readout rate of the system is high enough to track fluctuations in the beam intensity during one spill, such that the Mimotera could also serve as a tool for fast and reliable quality assurance in hadron therapy facilities